Measuring device for detecting a body moving in relation to a tubular container

ABSTRACT

The invention relates to a measuring device for detecting a body ( 3 ) moving in relation to an, in particular, tubular container ( 2 ). Said device comprises at least one magnet unit ( 4 - 9 ) which generates a magnetic field, measures this magnetic field and which is assigned to the container and/or to the magnetic body. The device also comprises at least one evaluation device connected to the magnet units and provided for receiving measurement signals of the magnet units. The aim of the invention is to improve a measuring device of this type in order to be able to easily determine, in addition to the position of the body ( 3 ) in relation to the container ( 2 ) in a longitudinal direction ( 33 ), the position of the body in relation to the container in the transverse direction with a relatively high level of accuracy. To this end, the magnet units comprise a maximum magnetic flux that is essentially perpendicular to the direction of the relative motion of the body and container.

[0001] This invention relates to a detection system for sensing anobject in motion relative to a container, especially tubular in design,whereby at least one magnetic unit is associated with the containerand/or object, generating as well as measuring magnetic fields, and atleast one evaluation device is connected to the magnetic units andserves to receive sensing signals from the magnetic units.

[0002] A detection system of this type is described in U.S. Pat. No.3,103,976. That particular detection system is used in locating pipes,and especially pipe ends to be joined, in underwater drilling andsimilar operations. A guide tube, serving as a container extendingbetween a topside derrick and a frame section anchored on the seabottom, is equipped on its outside with a coil as the magnetic unitgenerating a magnetic field and with each two search coils respectivelymounted above and below the first coil and serving as the magnetic-fieldmeasuring magnets. Electric cables connect these various coils with atopside evaluation unit within the derrick. Themagnetic-field-generating coil produces a magnetic field inside theguide tube essentially along the longitudinal axis of the tube. Thatmagnetic field also permeates the two magnetic-field-measuring coils. Ifand when within the guide tube a drill rod, tool, pipe or the like isshifted, the magnetic field in these measuring coils will change as afunction of the position of the moving object, leading to acorresponding induction in these coils. It is thus possible to determinewhen the object concerned has reached one of thesemagnetic-field-measuring coils or for instance the blowout valve locatedon the sea bottom.

[0003] That earlier detection system, however, is essentially limited tosensing the position only of the forward end of the moving object, withthe positional detection accuracy being determined by its distance fromthe coils which are mounted along the longitudinal axis of the guidetube, by the coil width in the longitudinal direction, and similarfactors.

[0004] It is the objective of this invention to provide an improveddetection system of the type first above mentioned, the improvementconsisting in the ability, in simple fashion and with a relatively highdegree of accuracy, to determine not only the position of the objectrelative to the container in the longitudinal direction but also itsposition in the transverse direction relative to the container.

[0005] In conjunction with the characteristic features specified withinthe main concept of claim 1, this is accomplished in that the magneticunits produce a maximum magnetic flux essentially perpendicular to thedirection of relative movement between the object and the container.This causes a change in the magnetic field and in the magnetic flux whenthe object is close enough to the container that both are located withinthe magnetic field of the magnetic-field-generating magnetic unit. Atthe same time, given this position of the object and the containerrelative to each other, there will be a change in the magnetic field inthe direction perpendicular to the relative movement, thus yielding forthe evaluation device additional information on the position of theobject and the container perpendicular to the direction of relativemovement.

[0006] According to this invention, the functionality of the detectionsystem does not depend on whether the container, for instance tubular indesign, is stationary while the object moves relative to it, or viceversa, for as long as at least the moving part contains a magneticelement which triggers a corresponding change in the magnetic fieldbetween the magnetic units.

[0007] In oil-drilling or similar operations, it may be advantageous inthis context if in particular the tubular container constitutes theaforementioned guide tube and the object is the part that moves relativeto that tube. The latter should consist of, or contain, a magneticmaterial at least at the point which is to serve for the detection ofthe position and orientation of the object relative to the container.That point could for instance be the forward end of the object.

[0008] An object of this type typically moves within the container sothat the corresponding magnetic units can be advantageously mounted inan inside area of the container. On the other hand, if the moving objectconsists of a non-magnetic material while the container is provided witha magnetic element in an appropriate location, the correspondingmagnetic units may equally well be mounted on an outside surface of theobject. It is also possible, for facilitated access, to position themagnetic units on an outside surface of the container with the generatedmagnetic field extending through the wall and into the interior of thecontainer.

[0009] In one possible, simple configuration for the precise capture ofthe moving object the magnetic units are arranged along at least oneorientational plane perpendicular to the direction of relative movement.For example, multiple magnetic units may be arranged in a circular arrayor in some other way depending on the cross-sectional shape of thecontainer, with the possibility of mounting the magnetic units, withequidistant spacing from one another, in the circumferential directionof the container.

[0010] So as not to limit the detection of the object to essentially onesuch plane, magnetic units may be mounted perpendicular to the directionof relative movement in evenly spaced planar increments. This permitscapture in each of these staggered planes as well as detection betweenthese planes by means of suitably interconnected magnetic units.

[0011] Depending on the design of the magnetic unit, it is possible forsuch a magnetic unit to be switchable between magnetic-field generationand magnetic-field sensing. This can take place even during the courseof a measurement. Evidently, such switchability of the magnetic unitsinvolves variable polarity of the magnetic units, variablemagnetic-field intensity or the like.

[0012] A simple design example of a magnetic-field-generating magneticunit can be implemented in the form of a permanent magnet.

[0013] For an expanded range of possibilities in object detection perthe above, a magnetic unit may be constituted of an electrically poweredcoil which provides a simple way to permit operation both formagnetic-field generation and magnetic-field measurement. A coil alsoallows for easy variation of the magnetic-field intensity or polarityand the generation of alternating fields.

[0014] A magnetic-field-measuring unit that is at once precise, simpleand inexpensive may be in the form of a magnetic-field sensor and inparticular a Hall element. Magnetic-field sensors of that type can beinstalled, in simple fashion and at low cost, in arrays of the desireddensity and configuration for instance on the inside of the container.

[0015] Of course, a suitably designed magnetic unit can also detectmagnetic attenuation instead of measuring the magnetic field or magneticflux.

[0016] For an amplification of the magnetic field and thus of themagnetic flux perpendicular to the direction of relative movement, themagnetic unit may incorporate a magnetizable material, for instance aferromagnetic or paramagnetic material.

[0017] To avoid having to separately provide each magnetic unit with amagnetizable material, the magnetic units may be interconnected by amagnetizable or magnetically conductive material.

[0018] For a secure installation of the magnetic unit, the unit may beplaced for instance in a radial bore in the container wall. The radialbore should be at least deep enough in the radial direction for themagnetic unit to be fully insertable without protruding into theinterior of the container.

[0019] To avoid having to drill a corresponding number of radial boresor similar recesses in the container wall while at the same time beingable to simultaneously manipulate a larger number of magnetic units, itis possible to mount multiple magnetic units in a magnetic-detectorinsert which may be mounted for instance in a circumferential recess onthe inside of the container. This recess can again be deep enough toprevent the magnetic-detector insert with the magnetic units fromprotruding into the interior of the container.

[0020] Suitably designed magnetic units allow for the deployment inobjects with a variety of cross sections. Of course, for oil explorationand similar applications it will be advantageous, and at the same timethe data capture for the detection of the object within the containerwill be simplified, if the container and/or object are essentiallytubular in design. In applications related to oil and gas exploration,it is an essentially tubular object that is guided within an equallymore or less tubular container. The object can be so guided that it iseither in contact with or moves at a distance from the inside wall ofthe container.

[0021] In another possible, simple and space-saving design, a magneticunit may be provided with a ramified and/or continuous helical,electrically conductive ribbon. Such a ribbon essentially corresponds toa coil and generates a comparable magnetic field.

[0022] For the convenient manipulation of ribbon-shaped magnetic unitsof this type, the ribbon may be mounted on a preferably annular insert.The insert, of course, is shaped to correspond to the cross section ofthe container, permitting easy installation on an inside surface of thecontainer.

[0023] The insert can allow for further simplification in that thenecessary electrical power-supply and/or signal-collecting leads areattached to the ribbon-shaped magnetic units mounted in the insert.

[0024] In analogous fashion it is possible in the case of theaforementioned magnetic-detector insert employing electrical coils toprovide the electric coils with winding stems as magnetic units. Thecoils are wound on these winding stems which, like the entiremagnetic-detector insert, may consist of a magnetizable material.

[0025] The evaluation especially of the signals received by themagnetic-field-sensing magnetic units is possible not only fordetermining the position of the object. A suitably equipped evaluationdevice may include a memory module and/or a display unit or may beconnectable to the latter or for instance to a computer. Stored in thememory module may be the necessary mathematical evaluation algorithmsand/or address tags permitting the analysis of the measured signals. Thedisplay unit may be used, for example, for a graphic illustration of theobject or for detecting the object.

[0026] The evaluation device may also be so configured that in additionto merely detecting the presence of the object it also permits thedetermination of the position, shape, size or direction of movement ofthe object.

[0027] The analysis of the signals emanating from the magnetic units andthe very positioning of the magnetic units can be simplified forinstance by aligning the magnetic axes of the magnetic units with alongitudinal axis of symmetry of the container.

[0028] The following describes desirable design examples of thisinvention in more detail with the aid of the figures in the attacheddrawings in which:

[0029]FIG. 1 is a perspective side view of a first design example of adetection system according to this invention, employing a tubularcontainer;

[0030]FIG. 2 is a top view of a horizontal section through FIG. 1;

[0031]FIG. 3 is a perspective side view of a second design example of adetection system according to this invention;

[0032]FIG. 4 shows a partial vertical section through FIG. 3;

[0033]FIG. 5 is a perspective side view of a third design example of adetection system according to this invention;

[0034]FIG. 6 is an enlarged illustration of detail “A” in FIG. 5;

[0035]FIG. 7 is an enlarged illustration of detail “B” in FIG. 5;

[0036]FIG. 8 is a conceptual illustration of a horizontal cross sectionthrough a detection system according to this invention;

[0037]FIG. 9 is an illustration as in FIG. 8 with an object in centralposition;

[0038]FIG. 10 is an illustration as in FIG. 8 with an object in anoff-center position;

[0039]FIG. 11 is an illustration as in FIG. 8 with an object in anotheroff-center position;

[0040]FIG. 12 is an illustration as in FIG. 8 with an object in anothercentral position;

[0041]FIG. 13 is a conceptual illustration explaining the magnetic flux;and

[0042]FIG. 14 shows in detail an area-array element per FIG. 13.

[0043]FIG. 1 depicts a first design example of a detection system 1according to this invention, with a tubular container 2 and a similarlytubular object 3. The container extends for instance from anocean-surface platform, not shown, to a frame section anchored on thesea floor. Inside the container 2 the object 3 is guided in thelongitudinal direction 33 i.e. in the direction of relative movement 14.The object may for instance be a section of a drill rod, a tool orsimilar implement employed in submarine oil exploration.

[0044] In an orientational plane 16 which extends perpendicular to thedirection of relative movement 14, the container 2 accommodates a numberof magnetic units 4 to 9. These are housed in corresponding radial boresof the container 2 and support at least one electric coil 17 each. Thecentral axes of the coils 17 are positioned in the orientational plane16 and point toward the center of the longitudinal bore 36. All magneticunits 4 to 9 are mounted in an equidistant relation to one another onthe inside 15 along the internal circumference of the container 2. Thecoils 17 are positioned within the radial bore 19 so that the magneticunits 5 to 9 will not protrude past the inner surface 15 into thelongitudinal bore 36.

[0045] Each coil 17 connects to the appropriate electrical leads 35which extend outward away from the container 2 from where they arebundled in omnibus cables, not shown, and run for instance to a topsidepoint.

[0046] At least magnetic unit 4 is a magnetic-field-generating magneticunit. Its magnetic field is modified by the object 3 which at least inpart consists of a magnetizable or magnetically conductive material 18,and the magnetic field, modified by the movement and changed position ofthe object 3 relative to the longitudinal bore 36, can be captured bythe magnetic-field-sensing magnetic units 6 to 9. By way of theirelectrical leads 35, the magnetic units 5 to 9 thus generate acorresponding induced voltage as a function of the magnetic fluxpermeating them and changing with time.

[0047] Instead of arranging the magnetic-field-generating magnetic unit4 and the corresponding magnetic-field-sensing magnetic units 5 to 9 inone single plane 16 per FIG. 1, it is also possible to position themagnetic-field-sensing magnetic units for instance partly or entirely indifferent orientational planes which are spaced at a distance from andoffset upward and/or downward relative to the orientational plane 16 perFIG. 1.

[0048]FIG. 2 shows a horizontal section through FIG. 1 in the area ofthe orientational plane 16 and more specifically in the area wheremagnetic unit 7 is located. The radial bore 19 in a wall 37 of thecontainer 2 opens toward the inside surface 15 while at its opposite enda wire duct 38 allows the electrical leads 35 to run from the coil 17 tothe outside and away from the longitudinal bore 36. The wire duct 38 canbe closed off with a cap 39 through which the leads 35 are passed via awater-tight seal.

[0049] The magnetic-field-generating magnetic unit 4 per FIG. 1 isconfigured in analogous fashion. It should be mentioned at this pointthat all magnetic units per FIG. 1 are capable of serving asmagnetic-field-generating or magnetic-field-sensing magnetic units. Forexample, magnetic units 6, 7 and 8 may be used as themagnetic-field-sensing units and the magnetic units 4, 5 and 9 as themagnetic-field-generating units. Obviously, any arbitrary assignment ofthese magnetic units is possible both before and during a givendetection process.

[0050]FIG. 3 is a perspective view, corresponding to FIG. 1, of a seconddesign example of the detection system 1 according to this invention. Inthis figure and in the figures that follow as well as in FIGS. 1 and 2,identical components bear identical reference numbers which will bementioned only occasionally.

[0051]FIG. 3 differs from FIG. 1 by the consolidation of the magneticunits 4 to 10 in one magnetic detection insert 20 consisting of amagnetizable or magnetically conductive material 18. The magneticdetection insert 20 is suitably mounted in a circumferential recess 21on the inside 15 of the wall 37 of the container 2. The magneticdetection insert 20 has an essentially U-shaped cross section. The openend of the U-profile faces inward in the direction of the longitudinalbore 36.

[0052] Located at given points in the annular gap 40 between the legs ofthe U-profile is a winding stem 28 consisting of a magnetizable materialand radially extending parallel with the U-legs toward the inside in thedirection of the longitudinal bore 36. Wound onto each such winding stem28 is a coil 17 of the respective magnetic unit 4 to 10. These magneticunits, i.e. coils, are arranged in one orientational plane 16 analogousto FIG. 1. It should be pointed out again that similar magneticdetection inserts can be mounted in more than one orientational plane.

[0053]FIG. 4 shows a partial vertical section through the design exampleper FIG. 3. It clearly illustrates that the coil 17 is wound on thewinding stem 28 and that the associated electrical leads 35 of the coil17 run through a hole in the wall 37 to the outside in a radialdirection relative to the container 2. As has been explained inconnection with FIG. 1, the various magnetic units 4 to 10 may beoptionally set to operate as magnetic-field-generating ormagnetic-field-sensing units.

[0054]FIG. 5 is a perspective view, analogous to FIGS. 1 and 3, of athird design example of the detection system according to thisinvention.

[0055] In this design example, the magnetic units 4 to 11 are in theform of ribbons 22 applied on an insert 23 by a thin-film or similartechnology process. The ribbons extend in a ramified and/or helicalconfiguration. Each ribbon is provided at one end with an electricalconnector 41 and at the other end with a corresponding electricalconnector 42 for supplying power or collecting sensing signals. On theoutside of the insert 23 opposite the longitudinal bore 36 the contacts41, 42 are connected, for instance as shown in FIG. 6, to electricalpower supply lines 24, 25 or electrical signal-processing lines 26, 27.These electrical lines 24, 25 and 26, 27 can be switched to serve eitheras power-supply or signal-processing lines, thus affording the option ofusing the magnetic units 4 to 11 either as magnetic-field-generating oras magnetic-field-sensing magnetic units.

[0056] The insert 23 consists of a thin ring of a magnetizable materialwhich allows easy mounting on the inside wall 15 of the container 2 inessentially any desired location. Similar inserts 23 can be mounted indifferent orientational planes as described in connection with FIGS. 1and 3.

[0057] At one point the insert 23, by way of its leads 24 to 27, isconnected to an evaluation device 12 which in the case of submarine oilexploration is typically located in a suitable place on a surfaceplatform. For other applications of the detection system according tothis invention, such as land-based oil exploration, the evaluationdevice 12 will be set up in a conveniently accessible location.

[0058] In the design example per FIG. 5, the evaluation device 12incorporates for instance a memory module 29 for saving the incomingsensing signals or for storing appropriate programs for the analysis ofthese sensing signals. The sensing signals, processed as necessary, canbe viewed on a display monitor 30 connected to the evaluation device 12.The evaluation device 12 may be computerized or connected to a remotecomputer 31 which may also allow the evaluation device to be programmedfor instance to switch the magnetic units into themagnetic-field-generating or respectively, magnetic-field-sensing mode.

[0059] At this juncture it should be mentioned that themagnetic-field-generating magnetic units may also be in the form ofpermanent magnets, for one example. The magnetic-field-sensing magneticunits on their part may be in the form of magnetic sensors such as Hallelements.

[0060] The evaluation device 12 also offers the possibility to changethe polarity or field intensity of the magnetic field generated.Alternating magnetic fields can also be produced.

[0061] FIGS. 8 to 12 are conceptual illustrations of the detectionsystem 1 according to this invention, showing different magnetic units 4to 11 without an object 3 (FIG. 8) and, respectively, with differentobjects in different positions within the container 2.

[0062]FIG. 8 shows the magnetic field generated by the magnetic unit 4,unaffected, as in FIG. 1, by any object 3. The correspondingmagnetic-field flux lines 43 extend perpendicular to the longitudinalbore 36 and flow to the respective magnetic-field-sensing magnetic units5 to 11. The distance of the magnetic-field-sensing magnetic units 5 to11 from the magnetic-field-generating magnetic unit 4 determines theextent to which the flux lines permeate the magnetic units. The magneticflux itself varies accordingly.

[0063] The magnetic units 4 to 11 are arranged in a way that they, andin particular their respective magnetic axes 32 as shown for instance inFIG. 9, are oriented toward a central point 34 in the longitudinal bore36, i.e. toward an axis of symmetry 34 which extends in the longitudinaldirection 33 per FIG. 1.

[0064] When an object 3 moves relative to the container 2, the resultwill be a change in the path of the magnetic flux lines, as shown inFIGS. 9 to 11. In FIG. 9 the object 3 is positioned at dead center 34,causing a correspondingly symmetrical flux-line distribution pattern. InFIG. 10, the object is situated off-center and close to themagnetic-field-generating magnetic unit 4.

[0065] In FIG. 11, the object 3 is again in an off-center position, inthis case close to the magnetic-field-sensing magnetic unit 9.

[0066] From the respective changes in the magnetic fields and themagnetic flux, detectable by the magnetic-field or magnetic-flux-sensingunits 5 to 11, conclusions can be drawn as to the presence of the object3 in the vicinity of the magnetic unit as well as the distance betweenthe object 3 and the individual magnetic units, the orientation anddimensions of the object 3 and its direction of movement. By means ofappropriate imaging processes in the evaluation device 12, for instanceas shown in FIG. 5, it is possible to view on the display monitor 30 theobject 3, its position, orientation, size and movement.

[0067]FIG. 12 shows an object 3 larger in overall dimensions and wallthickness, with corresponding changes in the magnetic field and magneticflux pattern. FIG. 12 thus shows what other conclusions are possible interms of the dimensions of the object 3.

[0068]FIG. 13 is a simplified representation of amagnetic-field-generating magnetic unit 4, the magnetic field and fluxline 43 generated by it, and the respective magnetic flux 13 throughdifferent area-array elements 44. Traditionally, the magnetic flux isdetermined by the following equation:$\Phi = {\int\limits_{\Delta}{B \times {A}}}$

[0069] where

[0070] Φ is the magnetic flux, B is the magnetic induction and dA is aninfinitesimal vectorial area-array element. According to the invention,the magnetic units 4 to 11 are so arranged that the respective magneticflux displays its maximum value perpendicular to the relative movementbetween the object and the container, meaning that the scalar productderived from magnetic induction and the vectorial area-array elementtakes on its maximum value for the respective area-array elements perFIG. 13.

[0071]FIG. 14 is a conceptual illustration showing that for eacharea-array element 44 the magnetic flux derives from the scalar productof magnetic induction B und ΔA as the vectorial area-array element. Theapplicable equation is a follows:

Φ=|B|×|ΔA|×cos α

[0072] where

[0073] α is the corresponding angle 46 between the vectors B and ΔA.

[0074] The following will briefly explain the operating mode of thedetection system according to this invention with reference to theattached drawings.

[0075] By way of the magnetic flux and/or the magnetic attenuation, thedetection system according to this invention measures any given objectof any given shape, orientation, position and geometry within a magneticfield generated inside a container 2. One or several magnetic unitsserve to generate the magnetic field and the corresponding magneticflux. One or several additional magnetic units capture the magnetic fluxthat has been modified by the object and its movement or location and onthe basis of the sensing signals received it is possible to determinethe distance between the object and these magnetic units as well as theposition, size and direction of movement of the object. Themagnetic-flux-based measurement can take place in static and/or dynamicfashion through alternating fields, variable field intensity andvariable polarity. The magnetic-field-generating magnetic units may bein the form for instance of a permanent magnet or electrically poweredand controlled coil. The magnetic-field-sensing magnetic units canmeasure the magnetic flux produced in static fashion employing Hallelements and/or in dynamic fashion by way of electromagnetic induction.The configuration and the number of the magnetic-field-generating andmagnetic-field-sensing magnetic units are variable, and especially whencoils are used as the magnetic units a switchover between themagnetic-field-generating and the magnetic-field-sensing mode of themagnetic units is easily accomplished.

[0076] The sensing signals are evaluated using mathematical operationsand/or address tags and it is possible to display them in graphic formon a display monitor per FIG. 5, showing the shape and position of theobject under analysis.

[0077] The magnetic units can be arranged in a circular or otherconfiguration in one or several planes and they are typicallyinterconnected via a magnetically conductive or magnetizable material.The multiplicity of the different magnetic units and their utilizationfor generating or sensing and measuring magnetic fields produce magneticflux patterns between all associated magnetic units which patterns, andany changes thereof, are used for the imaging and positionaldetermination of the object to be measured. The varying magnetic flux isanalyzed by appropriate metrics for a determination of the size, shapeand position of drill pipes including their tool joints and anyassociated tools. It is also possible to detect the direction when thepipes or tools constituting the objects within the tubular container aremoved. The magnetic units can further recognize drill pipes which are incontact with one of the inside walls of the container, causing thedreaded friction-induced wash-out of the equipment.

1. Detection system (1) for sensing an object (3) in motion relativeespecially to a tubular container (2), with at least onemagnetic-field-generating and magnetic-field-sensing magnetic unit(5-11) associated with the container (2) and/or object (3), and with atleast one evaluation device (12) connected to the magnetic units (5-11)for receiving sensing signals from the magnetic units, characterized inthat the maximum magnetic flux (13) of the magnetic units (5-11) runsessentially perpendicular to the direction (14) of the relative movementbetween the object (3) and the container (2).
 2. Detection system as inclaim 1, characterized in that the object (3) consists at least in partof a magnetic material.
 3. Detection system as in claim 1 or 2,characterized in that the magnetic units (5-11) are positioned in aninside-surface area (15) of the container (2).
 4. Detection system as inat least one of the above claims, characterized in that the magneticunits (5-11) are positioned in at least one orientational plane (16)perpendicular to the direction of relative movement (14).
 5. Detectionsystem as in at least one of the above claims, characterized in that themagnetic units (5-11) are positioned in orientational planes (16) whichare spaced apart in the direction of relative movement (14) and extendperpendicular to said direction of relative movement (14).
 6. Detectionsystem as in at least one of the above claims, characterized in that themagnetic unit (5-11) is switchable between magnetic-field generation andmagnetic-field sensing.
 7. Detection system as in at least one of theabove claims, characterized in that the magnetic-field-generatingmagnetic unit (5-11) is a permanent magnet.
 8. Detection system as in atleast one of the above claims, characterized in that the magnetic unit(5-11) is an electrically powered coil (17).
 9. Detection system as inat least one of the above claims, characterized in that themagnetic-field sensing unit (5-11) is a magnetic-field sensor and inparticular a Hall element.
 10. Detection system as in at least one ofthe above claims, characterized in that a magnetic attenuation can bedetected by the magnetic-field-sensing magnetic unit (5-11). 11.Detection system as in at least one of the above claims, characterizedin that the magnetic unit (5-11) incorporates a magnetizable material.12. Detection system as in at least one of the above claims,characterized in that the magnetic units (5-11) are interconnected bymeans of a magnetizable material.
 13. Detection system as in at leastone of the above claims, characterized in that the magnetic unit (5-11)is positioned in a radial bore (19) provided in the container (2). 14.Detection system as in at least one of the above claims, characterizedin that a number of magnetic units (5-11) are mounted on a magneticdetection insert (20) which can be inserted in a circumferential recess(21) on the inside (15) of the container (2).
 15. Detection system as inat least one of the above claims, characterized in that the container(2) and/or the object (3) are essentially tubular in design and/or areguided one inside the other.
 16. Detection system as in at least one ofthe above claims, characterized in that the magnetic unit (5-11)features a continuous ramified and/or helical, electrically conductiveribbon (22).
 17. Detection system as in at least one of the aboveclaims, characterized in that the ribbon (22) is mounted on an annularinsert (23).
 18. Detection system as in at least one of the aboveclaims, characterized in that electrical wires (24-27) are attached tothe ribbon shaped magnetic unit (5-11) for supplying power to and/orcollecting signals from the ribbon-shaped magnetic unit (5-11). 19.Detection system as in at least one of the above claims, characterizedin that the magnetic detection insert (20) is provided with windingstems (28) for electrical coils (17).
 20. Detection system as in atleast one of the above claims, characterized in that the evaluationdevice (12) incorporates a memory module (29) and/or a display unit (30)and/or permits connection to a computer (31).
 21. Detection system as inat least one of the above claims, characterized in that a magnetic axis(32) of the magnetic unit (5-11) points to an axis of symmetry (34)extending in the longitudinal direction (33) of the container (2). 22.Detection system as in at least one of the above claims, characterizedin that by means of the evaluation device (12) it is possible todetermine the presence and/or position and/or direction of movementand/or size of the object (3).